Topic Two

Biogeochemical Cycles

2-2 Water Cycle

Water Cycle Water cycle path of water through the

environment From the earth to the atmosphere and back to

the earth Importance of water:

Absorbs and releases water-stable global weather patterns

Medium for reactions Solvent 60% of cell’s mass

Water’s Role Moves from atmosphere to earth through

precipitation Surface runoff and groundwater flows to other

bodies of water Water enters the atmosphere through

transpiration evaporation Transpiration: loss of water thru leaves of plants

Role of living things Plants:

Return water to the atmosphere through transpiration and evaporation

Animals: Return water to the atmosphere through gas

exchange, perspiration, evaporation, excretion

Acid Rain Caused by release of nitrogen and sulphur

compounds into the atmosphere Change into acidic compounds and rain down lowers pH causing aquatic life to experience

chemical "shock" effects EG. Success of trout eggs is decreased when pH

falls below 5.5 reduces crop productivity and forest growth

rates Increases amount of metals water from soil accelerates weathering of limestone surfaces

on buildings and monuments; corrodes metals

Acid Rain

Water Cycle

Water Cycle

1 Water in clouds

2 Rain and snow

3 Water drains into river and soil

4 Water taken up by plants and animals

5 Water loss by transpiration

6 Water loss by respiration

7 Evaporation